U.S. patent application number 12/280812 was filed with the patent office on 2009-05-28 for optical pickup, optical element, optical information device, computer, optical information medium player, car navigation system, optical information medium recorder and optical disk server.
This patent application is currently assigned to Matsushita Electric Industrial Co., Ltd.. Invention is credited to Yoshiaki Komma, Keiichi Matzuzaki, Kousei Sano, Toshiyasu Tanaka, Hidenori Wada, Kanji Wakabayashi.
Application Number | 20090138901 12/280812 |
Document ID | / |
Family ID | 38459068 |
Filed Date | 2009-05-28 |
United States Patent
Application |
20090138901 |
Kind Code |
A1 |
Tanaka; Toshiyasu ; et
al. |
May 28, 2009 |
OPTICAL PICKUP, OPTICAL ELEMENT, OPTICAL INFORMATION DEVICE,
COMPUTER, OPTICAL INFORMATION MEDIUM PLAYER, CAR NAVIGATION SYSTEM,
OPTICAL INFORMATION MEDIUM RECORDER AND OPTICAL DISK SERVER
Abstract
An optical pickup includes: a laser light source which outputs
an divergent beam having an elliptical far-field pattern; a beam
shaping element having at least one cylindrical plane and which
shapes the divergent beam outputted from the laser light source
into an divergent beam having a prescribed shape in which at least
the length in the major axis direction of the elliptical shape is
shortened; a light collecting portion having a beam splitter which
perpendicularly collects the divergent beam that is outputted from
the beam shaping element and which has a prescribed shape on the
recording surface of an optical disk, and a mirror or the like; and
a light detecting portion The optical axis of the divergent beam is
rotated so that the direction in which the major axis of the
divergent beam having a prescribed shape is shortened conforms to
the radial direction of an optical information recording
medium.
Inventors: |
Tanaka; Toshiyasu; (Osaka,
JP) ; Komma; Yoshiaki; (Osaka, JP) ; Sano;
Kousei; (Osaka, JP) ; Wada; Hidenori; (Kyoto,
JP) ; Matzuzaki; Keiichi; (Osaka, JP) ;
Wakabayashi; Kanji; (Kyoto, JP) |
Correspondence
Address: |
RATNERPRESTIA
P.O. BOX 980
VALLEY FORGE
PA
19482
US
|
Assignee: |
Matsushita Electric Industrial Co.,
Ltd.
Osaka
JP
|
Family ID: |
38459068 |
Appl. No.: |
12/280812 |
Filed: |
February 27, 2007 |
PCT Filed: |
February 27, 2007 |
PCT NO: |
PCT/JP2007/053660 |
371 Date: |
August 27, 2008 |
Current U.S.
Class: |
720/659 ;
345/156; 369/112.01; 701/532; G9B/7; G9B/7.112 |
Current CPC
Class: |
G11B 7/1392 20130101;
G11B 7/1398 20130101 |
Class at
Publication: |
720/659 ;
345/156; 369/112.01; 701/200; G9B/7; G9B/7.112 |
International
Class: |
G11B 7/135 20060101
G11B007/135; G11B 7/00 20060101 G11B007/00; G01C 21/00 20060101
G01C021/00; G09G 5/00 20060101 G09G005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 28, 2006 |
JP |
2006-054071 |
Claims
1.-14. (canceled)
15. An optical information device comprising: an optical head
device including the optical pickup according to claim 21; a motor
which rotates the optical information recording medium; and an
electrical circuit which controls and drives the motor, an optical
lens and the light source based on a signal obtained from the
optical head device.
16. A computer comprising: the optical information device according
to claim 15; an input device or an input terminal for inputting
information; a computing device which performs computations based
on information inputted from the input device or the input terminal
and/or information reproduced from the optical information device;
and an output device or an output terminal for displaying or
outputting information inputted from the input device or the input
terminal and/or information reproduced from the optical information
device and/or a result of a computation performed by the computing
device.
17. An optical information medium player comprising: the optical
information device according to claim 15; and an
information-to-image decoder which converts an information signal
obtained from the optical information device to an image.
18. A car navigation system comprising: the optical information
device according to claim 15; and an information-to-image decoder
which converts an information signal obtained from the optical
information device to an image.
19. An optical information medium recorder comprising: the optical
information device according to claim 15; and an
image-to-information encoder which converts image information to
information to be recorded by the optical information device.
20. An optical disk server comprising: the optical information
device according to claim 15; and an input/output terminal which
exchanges information with the outside.
21. An optical pickup for use with a light source which emits a
divergent beam having an elliptical far-field pattern, the optical
pickup comprising: a beam shaping element having at least one
cylindrical plane and which shapes the divergent beam outputted
from the light source into an divergent beam having a prescribed
shape in which at least the length in the major axis direction of
the elliptical shape is shortened; a light collecting portion which
collects the divergent beam having the prescribed shape, which is
shaped by the beam shaping element shape on the recording surface
of an optical information recording medium so that the optical axis
of the divergent beam is perpendicular to the recording surface; a
light detecting portion which detects a beam reflected on the
optical information recording medium; a mounting plate on which the
beam shaping element is to be mounted; an optical axis adjustment
holder provided at a position fixed with respect to the light
collecting portion and to which the light source is attached; and a
light source tilting holder connected to the optical axis
adjustment holder so as to be rotationally movable and to which the
mounting plate is fixed, wherein a position of the optical axis of
the elliptical divergent beam emitted from the light source with
respect to the light collecting portion is adjusted by a rotational
movement of the light source tilting holder, and the light source
tilting holder is adjusted to a position at which an angle formed
by the generating line of the cylindrical plane of the beam shaping
element and the recording surface of the optical information
recording medium becomes equal to the sum of an angle of an
emission angle gradient of the elliptical shape of the divergent
beam outputted from the light source in the minor axis direction
and a right angle.
22. The optical pickup according to claim 21, further comprising: a
first outer shell portion provided so as to cover a part of the
periphery of the beam shaping element the first outer shell portion
being fixed to a part of the periphery of a side wall of the beam
shaping element; and a second outer shell portion provided so as to
cover a part of the periphery of the first outer shell portion and
a part of the periphery of the beam shaping element, the second
outer shell portion including a contact portion at which the second
outer shell portion comes into contact with a part of the periphery
of the first outer shell portion and another part of the periphery
of the side wall of the beam shaping element so as to be slidingly
movable, wherein the second outer shell portion includes a gap
which exposes the surface of the first outer shell portion to the
outside, the first outer shell portion includes a knob portion
which protrudes from the gap of the second outer shell portion and
can be operated from the outside, the contact portion of the second
outer shell portion has a structure regulating the beam shaping
element so as to prevent the beam shaping element from moving in a
direction perpendicular to the optical axis direction thereof, and
the beam shaping element is mounted to the mounting plate via the
second outer shell portion.
23. The optical pickup according to claim 22, wherein the contact
portion of the second outer shell portion includes a first side
wall which comes into plane contact with the first outer shell
portion, a second side wall which applies elastic force to the
first outer shell portion, and a third side wall which comes into
either point contact or line contact with the beam shaping element,
the first side wall, the second side wall and the third side wall
are formed in a direction parallel to the optical axis of the beam
shaping element, and the gap is provided on the second side
wall.
24. The optical pickup according to claim 22, wherein of the first
outer shell portion and the second outer shell portion, paint is
applied to at least a part at which the first side wall of the
contact portion of the second outer shell portion comes into
contact with the first outer shell portion, and a part at which the
third side wall of the contact portion of the second outer shell
portion comes into contact with the beam shaping element.
25. The optical pickup according to claim 24, wherein the contact
portion of the second outer shell portion includes a first side
wall which comes into plane contact with the first outer shell
portion, a second side wall which applies elastic force to the
first outer shell portion, and a third side wall which comes into
either point contact or line contact with the beam shaping element,
the first side wall, the second side wall and the third side wall
are formed in a direction parallel to the optical axis of the beam
shaping element, and the gap is provided on the second side
wall.
26. The optical pickup according to claim 22, wherein the second
outer shell portion comprises the two members of: a beam shaping
element holder including the first side wall and the third side
wall; and an elastic body including the second side wall, further
wherein the elastic body and the beam shaping elements holder
sandwich the mounting plate so as to come into contact with each
other.
27. The optical pickup according to claim 21, wherein the beam
shaping element is fixed to the mounting plate by an adhesive.
28. The optical pickup according to claim 21, wherein the light
source tilting holder and the mounting plate are integrally
formed.
29. The optical pickup according to claim 21, wherein the beam
shaping element is fixed to the light source tilting holder by an
adhesive.
30. The optical pickup according to claim 21, wherein a contraction
rate of the elliptical shape during the shaping by the light
collecting portion is smaller than an emission angle ratio of the
light source.
31. An optical pickup for use with a light source which emits a
divergent beam having an elliptical far-field pattern, the optical
pickup comprising: a beam shaping element having at least one
cylindrical plane and which shapes the divergent beam outputted
from the light source into an divergent beam having a prescribed
shape in which at least the length in the major axis direction of
the elliptical shape is shortened; a light collecting portion which
collects the divergent beam having the prescribed shape, which is
shaped by the beam shaping element shape on the recording surface
of an optical information recording medium so that the optical axis
of the divergent beam is perpendicular to the recording surface; a
light detecting portion which detects a beam reflected on the
optical information recording medium; an optical axis adjustment
holder provided at a position fixed with respect to the light
collecting portion and to which the light source is attached; a
light source tilting holder connected to the optical axis
adjustment holder so as to be rotationally movable and to which the
mounting plate is fixed; and an optical base on which the light
collecting portion is disposed, wherein a recessed portion or a
through-hole is formed on the optical base, a position of the
optical axis of the elliptical divergent beam emitted from the
light source with respect to the light collecting portion is
adjusted by a rotational movement of the light source tilting
holder, and the light source tilting holder is adjusted to a
position at which an angle formed by the generating line of the
cylindrical plane of the beam shaping element and the recording
surface of the optical information recording medium becomes equal
to the sum of an angle of an emission angle gradient of the
elliptical shape of the divergent beam outputted from the light
source in the minor axis direction and a right angle.
32. An optical pickup for use with a light source which emits a
divergent beam having an elliptical far-field pattern, the optical
pickup comprising: a beam shaping element having at least one
cylindrical plane and which shapes the divergent beam emitted from
the light source into an divergent beam having a prescribed shape
in which at least the length in the major axis direction of the
elliptical shape is shortened; a light collecting portion which
collects the divergent beam having the prescribed shape, which is
shaped by the beam shaping element shape on the recording surface
of an optical information recording medium so that the optical axis
of the divergent beam is perpendicular to the recording surface; a
light detecting portion which detects the beam reflected on the
optical information recording medium, wherein the light collecting
portion rotates the optical axis of the divergent beam so that the
direction in which the major axis of the divergent beam having a
prescribed shape is shortened conforms to the radial direction of
the optical information recording medium.
33. The optical pickup according to claim 32, wherein a contraction
rate of the elliptical shape during the shaping by the light
collecting portion is smaller than an emission angle ratio of the
light source.
34. The optical pickup according to claim 32, wherein a width of a
divergent beam having the prescribed shape after subjected to
shaping by the beam shaping element in the same direction as the
major axis direction of the divergent beam having the elliptical
shape prior to shaping is longer than a width in the same direction
as the minor axis direction of the divergent beam having the
elliptical shape prior to shaping.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a U.S. national phase application of PCT
International Patent Application No. PCT/JP2007/053660 filed Feb.
27, 2007 claiming the benefit of priority of Japanese Patent
Application No. 2006-054071 filed Feb. 28, 2006, all of which are
incorporated by reference herein in their entirety.
TECHNICAL FIELD
[0002] The present invention relates to an optical pickup, an
optical element, an optical information device, a computer, an
optical information medium player, a car navigation system, an
optical information medium recorder and an optical disk server
which emit light from the optical pickup to an optical information
recording medium to record and/or reproduce information.
BACKGROUND ART
[0003] There are various recording media for recording and storing
digital audio, images, videos, and document files or data files
created on a computer. One of such media is an optical disk. In
particular, DVDs (Digital Versatile Disks) have a higher density
and a greater capacity than conventional CDs (Compact Discs), and
are becoming popular in the field of recording devices as the
medium to succeed currently dominant VTRs (Video Tape Recorders).
Furthermore, in recent years, research on next-generation optical
disks which use a blue-violet semiconductor laser and feature
further improved recording density is being carried out at various
locations, and its early appearance and penetration are
anticipated. Moreover, recording/reproducing data with such optical
disks require an optical pickup device.
[0004] Generally, an optical pickup that records or reproduces
information on an optical disk includes a light source, an
objective lens that causes a beam outputted from the light source
to be collected on the optical disk, and a detector that detects a
beam reflected off of the optical disk.
[0005] With a semiconductor laser as the light source, since a beam
is emitted from an edge face of a thin active layer, the
cross-sectional shape of a beam or, in other words, the shape as
seen from an optical axis direction has an elliptical shape having
a minor-to-major axis ratio of approximately 1:3. When recording
information onto an optical disk, an elliptical beam is desirably
shaped into a circular shape from the perspective of improving
light use efficiency.
[0006] An anomorphic prism or an anomorphic lens is generally used
as such beam shaping elements. However, since an anomorphic prism
must be used in a parallel light beam obtained by collimating
diverging light outputted from a semiconductor laser, downsizing of
optical pickups is inhibited. In consideration thereof, by using an
anomorphic lens capable of performing beam shaping on a divergent
light beam, an increased light use efficiency and a smaller-sized
optical pickup can be realized.
[0007] On the other hand, other elements that actually constitute
an optical pickup include a reflective optical element and an
objective lens. However, these elements may generally have
astigmatism as an initial characteristic. While a beam shaping
element featuring an anomorphic lens characteristically generates
astigmatism due to a displacement from a luminous point with
respect to a design value, an optical pickup conversely takes
advantage of this characteristic and is capable of correcting
astigmatism existing in a reflective optical element or an
objective lens. Such a configuration enables the quality of spots
outputted from the objective lens of an optical pickup and formed
on the optical disk to be improved.
[0008] FIG. 24 shows a diagrammatic explanatory drawing depicting a
configuration of a light source portion of a conventional example
of a beam shaping element retaining structure (for example, refer
to Japanese Patent Laid-Open No. 2003-178480). FIGS. 24(a) and
24(b) respectively represent an xz cross-sectional view and a yz
cross-sectional view.
[0009] In the present specification, a direction parallel to the
optical axis as seen from a luminous point of the light source
shall be referred to as a +z direction, a direction perpendicular
to the optical axis and parallel to an optical recording medium as
seen from the luminous point shall be referred to as a .+-.x
direction, and a direction perpendicular to both the optical axis
and the optical recording medium as seen from the luminous point
shall be referred to as a .+-.y direction. Furthermore, it is
assumed that the x axis, the y axis and the z axis are
perpendicular to each other.
[0010] The light source portion disclosed in Japanese Patent
Laid-Open No. 2003-178480
[0011] includes a semiconductor laser P that emits an elliptical
divergent beam; a beam shaping element L that converts an
elliptical divergent beam emitted from the semiconductor laser P
into an approximately circular divergent beam; and a retaining
member H that integrally retains the semiconductor laser P and the
beam shaping element L.
[0012] The beam shaping element L is constituted by a cylinder face
whose first face (S1) and second face (S2) are both curved only in
the x direction, wherein both cylinder faces (S1, S2) are curved so
as to be a concave face with respect to the semiconductor laser P
only on cross sections having smaller capture angles from the
semiconductor laser P (i.e., xz cross sections).
[0013] The light source portion of the conventional example
described above is designed so as to be able to provide a light
source device capable of outputting an light beam that diverges
while retaining an approximately circular shape and suppressing
wavefront aberrations due to changes in environmental temperature
by equalizing distances s and t shown in FIGS. 24(a) and 24(b) and
by equalizing linear expansion coefficients of the beam shaping
element L and the retaining member H.
[0014] Moreover, stable configurations of a beam shaping element
include the example described in Japanese Patent Laid-Open No.
2004-247032. This configuration is provided with a shape in which
both an incident plane and an output plane are cylindrical planes,
and shapes an incident beam having an elliptically shaped cross
section into an approximately circular shape by expanding a minor
axis direction thereof while retaining its major axis size.
DISCLOSURE OF THE INVENTION
[0015] Regarding the practical use of a high-density optical disk
using a laser, special emphasis is placed on RIM intensity. A RIM
intensity is a ratio of the intensity at a rim with respect to an
optical maximum intensity of a light beam having passed an aperture
in the vicinity of an objective lens of an optical pickup. An
increased RIM intensity is important in improving
recording/reproducing quality of information on a high-density
optical disk.
[0016] However, the conventional optical pickups described in each
of the above patent documents do not consider a beam shaping method
by a beam shaping element or the position of the beam shaping
element within the optical pickup from the perspective of adjusting
and increasing RIM intensity.
[0017] The present invention has been made in order to solve the
above problem, and an object of the present invention is to provide
an optical pickup, an optical element, an optical information
device, a computer, an optical information medium player, a car
navigation system, an optical information medium recorder and an
optical disk server intended to adjust/increase RIM intensity using
a beam shaping element.
Means to Solve the Problems
[0018] The 15.sup.th aspect of the present invention is an optical
information device comprising:
[0019] an optical head device including the optical pickup
according to the 21.sup.st aspect of the present invention;
[0020] a motor which rotates the optical information recording
medium; and
[0021] an electrical circuit which controls and drives the motor,
an optical lens and the light source based on a signal obtained
from the optical head device.
[0022] The 16.sup.th aspect of the present invention is a computer
comprising:
[0023] the optical information device according to the 15.sup.th
aspect of the present invention;
[0024] an input device or an input terminal for inputting
information;
[0025] a computing device which performs computations based on
information inputted from the input device or the input terminal
and/or information reproduced from the optical information device;
and
[0026] an output device or an output terminal for displaying or
outputting information inputted from the input device or the input
terminal and/or information reproduced from the optical information
device and/or a result of a computation performed by the computing
device.
[0027] The 17.sup.th aspect of the present invention is an optical
information medium player comprising:
[0028] the optical information device according to the 15.sup.th
aspect of the present invention; and
[0029] an information-to-image decoder which converts an
information signal obtained from the optical information device to
an image.
[0030] The 18.sup.th aspect of the present invention is a car
navigation system comprising:
[0031] the optical information device according to the 15.sup.th
aspect of the present invention; and
[0032] an information-to-image decoder which converts an
information signal obtained from the optical information device to
an image.
[0033] The 19.sup.th aspect of the present invention is an optical
information medium recorder comprising:
[0034] the optical information device according to The 15.sup.th
aspect of the present invention; and
[0035] an image-to-information encoder which converts image
information to information to be recorded by the optical
information device.
[0036] The 20.sup.th aspect of the present invention is an optical
disk server comprising:
[0037] the optical information device according to The 15.sup.th
aspect of the present invention; and
[0038] an input/output terminal which exchanges information with
the outside.
[0039] The 21.sup.st aspect of the present invention is an optical
pickup comprising:
[0040] a light source which emits a divergent beam having an
elliptical far-field pattern;
[0041] a beam shaping element having at least one cylindrical plane
and which shapes the divergent beam outputted from the light source
into an divergent beam having a prescribed shape in which at least
the length in the major axis direction of the elliptical shape is
shortened;
[0042] a light collecting portion which collects the divergent beam
having the prescribed shape, which is shaped by the beam shaping
element shape on the recording surface of an optical information
recording medium so that the optical axis of the divergent beam is
perpendicular to the recording surface;
[0043] a light detecting portion which detects a beam reflected on
the optical information recording medium;
[0044] a mounting plate on which the beam shaping element is to be
mounted;
[0045] an optical axis adjustment holder provided at a position
fixed with respect to the light collecting portion and to which the
light source is attached; and
[0046] a light source tilting holder connected to the optical axis
adjustment holder so as to be rotationally movable and to which the
mounting plate is fixed, wherein
[0047] a position of the optical axis of the elliptical divergent
beam emitted from the light source with respect to the light
collecting portion is adjusted by a rotational movement of the
light source tilting holder, and
[0048] the light source tilting holder is adjusted to a position at
which an angle formed by the generating line of the cylindrical
plane of the beam shaping element and the recording surface of the
optical information recording medium becomes equal to the sum of an
angle of an emission angle gradient of the elliptical shape of the
divergent beam outputted from the light source in the minor axis
direction and a right angle.
[0049] The 22.sup.nd aspect of the present invention is the optical
pickup according to the 21.sup.st aspect of the present invention,
further comprising:
[0050] a first outer shell portion provided so as to cover a part
of the periphery of the beam shaping element the first outer shell
portion being fixed to a part of the periphery of a side wall of
the beam shaping element; and
[0051] a second outer shell portion provided so as to cover a part
of the periphery of the first outer shell portion and a part of the
periphery of the beam shaping element, the second outer shell
portion including a contact portion at which the second outer shell
portion comes into contact with a part of the periphery of the
first outer shell portion and another part of the periphery of the
side wall of the beam shaping element so as to be slidingly
movable; wherein
[0052] the second outer shell portion includes a gap which exposes
the surface of the first outer shell portion to the outside,
[0053] the first outer shell portion includes a knob portion which
protrudes from the gap of the second outer shell portion and can be
operated from the outside,
[0054] the contact portion of the second outer shell portion has a
structure regulating the beam shaping element so as to prevent the
beam shaping element from moving in a direction perpendicular to
the optical axis direction thereof, and
[0055] the beam shaping element is mounted to the mounting plate
via the second outer shell portion.
[0056] The 23.sup.rd aspect of the present invention is the optical
pickup according to the 22.sup.nd aspect of the present invention,
wherein
[0057] the contact portion of the second outer shell portion
includes a first side wall which comes into plane contact with the
first outer shell portion, a second side wall which applies elastic
force to the first outer shell portion, and a third side wall which
comes into either point contact or line contact with the beam
shaping element,
[0058] the first side wall, the second side wall and the third side
wall are formed in a direction parallel to the optical axis of the
beam shaping element, and
[0059] the gap is provided on the second side wall.
[0060] The 24.sup.th aspect of the present invention is the optical
pickup according to the 22.sup.nd aspect of the present invention,
wherein
[0061] of the first outer shell portion and the second outer shell
portion, paint is applied to at least
[0062] a part at which the first side wall of the contact portion
of the second outer shell portion comes into contact with the first
outer shell portion, and a part at which the third side wall of the
contact portion of the second outer shell portion comes into
contact with the beam shaping element.
[0063] The 25.sup.th aspect of the present invention is the optical
pickup according to the 24.sup.th aspect of the present invention,
wherein
[0064] the contact portion of the second outer shell portion
includes a first side wall which comes into plane contact with the
first outer shell portion, a second side wall which applies elastic
force to the first outer shell portion, and a third side wall which
comes into either point contact or line contact with the beam
shaping element,
[0065] the first side wall, the second side wall and the third side
wall are formed in a direction parallel to the optical axis of the
beam shaping element, and
[0066] the gap is provided on the second side wall.
[0067] The 26.sup.th aspect of the present invention is the optical
pickup according to the 22.sup.nd aspect of the present invention,
wherein
[0068] the second outer shell portion comprises the two members
of:
[0069] a beam shaping element holder including the first side wall
and the third side wall; and
[0070] an elastic body including the second side wall, further
wherein
[0071] the elastic body and the beam shaping elements holder
sandwich the mounting plate so as to come into contact with each
other.
[0072] The 27.sup.th aspect of the present invention is the optical
pickup according to the 21.sup.st aspect of the present invention,
wherein the beam shaping element is fixed to the mounting plate by
an adhesive.
[0073] The 28.sup.th aspect of the present invention is the optical
pickup according to the 21.sup.st aspect of the present invention,
wherein the light source tilting holder and the mounting plate are
integrally formed.
[0074] The 29.sup.th aspect of the present invention is the optical
pickup according to the 21.sup.st aspect of the present invention,
wherein the beam shaping element is fixed to the light source
tilting holder by an adhesive.
[0075] The 30.sup.th aspect of the present invention is the optical
pickup according to the 21.sup.st aspect of the present invention,
comprising:
[0076] an optical base on which the light collecting portion is
disposed, wherein
[0077] a recessed portion or a through-hole is formed on the
optical base in which a part of the mounting plate and members
mounted on the mounting plate is capable of moving when performing
tilting adjustment on the light source tilting holder.
[0078] The 31.sup.st aspect of the present invention is an optical
pickup comprising:
[0079] a light source which emits a divergent beam having an
elliptical far-field pattern;
[0080] a beam shaping element having at least one cylindrical plane
and which shapes the divergent beam emitted from the light source
into an divergent beam having a prescribed shape in which at least
the length in the major axis direction of the elliptical shape is
shortened;
[0081] a light collecting portion which collects the divergent beam
having the prescribed shape, which is shaped by the beam shaping
element shape on the recording surface of an optical information
recording medium so that the optical axis of the divergent beam is
perpendicularly to the recording surface;
[0082] a light detecting portion which detects the beam reflected
on the optical information recording medium, wherein
[0083] the light collecting portion rotates the optical axis of the
divergent beam so that the direction in which the major axis of the
divergent beam having a prescribed shape is shortened conforms to
the radial direction of the optical information recording
medium.
[0084] The 32.sup.nd aspect of the present invention is the optical
pickup according to the 21.sup.st aspect of the present invention,
wherein a contraction rate of the elliptical shape during the
shaping by the light collecting portion is smaller than an emission
angle ratio of the light source.
[0085] The 33.sup.rd aspect of the present invention is the optical
pickup according to the 21.sup.st aspect of the present invention,
wherein a contraction rate of the elliptical shape during the
shaping by the light collecting portion is smaller than an emission
angle ratio of the light source.
[0086] The 34.sup.th aspect of the present invention is the optical
pickup according to the 21.sup.st aspect of the present invention,
wherein a width of a divergent beam having the prescribed shape
after subjected to shaping by the beam shaping element in the same
direction as the major axis direction of the divergent beam having
the elliptical shape prior to shaping is longer than a width in the
same direction as the minor axis direction of the divergent beam
having the elliptical shape prior to shaping.
ADVANTAGE OF THE INVENTION
[0087] The present invention provides an optical pickup, an optical
element, an optical information device, a computer, an optical
information medium player, a car navigation system, an optical
information medium recorder and an optical disk server capable of
adjusting/increasing RIM intensity using a beam shaping
element.
BRIEF DESCRIPTION OF THE DRAWINGS
[0088] FIG. 1(a) is a diagrammatic explanatory drawing showing a
configuration of an optical pickup according to a first embodiment
of the present invention;
[0089] FIG. 1(b) is an explanatory drawing showing a configuration
of the vicinity of an objective lens of the optical pickup
according to the first embodiment of the present invention;
[0090] FIG. 1(c) is an enlarged configuration diagram of a beam
shaping element of the optical pickup according to the first
embodiment of the present invention;
[0091] FIG. 1(d) is a diagram for explaining the effects of the
beam shaping element of the optical pickup according to the first
embodiment of the present invention;
[0092] FIG. 2(a) is a diagrammatic explanatory drawing showing
another configuration of the optical pickup according to the first
embodiment of the present invention, and FIG. 2(b) is an enlarged
configuration diagram showing the other configuration example of
the beam shaping element of the optical pickup according to the
first embodiment of the present invention;
[0093] FIG. 3 is a diagrammatic explanatory drawing showing a
configuration in which the first embodiment of the present
invention has been used in an optical pickup having a
multi-wavelength light source;
[0094] FIG. 4(a) is a diagrammatic explanatory drawing showing a
configuration of a beam shaping element fixing portion of an
optical pickup according to a second embodiment of the present
invention, and FIG. 4(b) is an xz cross section and an yz cross
section of the beam shaping element of the optical pickup according
to the second embodiment of the present invention;
[0095] FIG. 5(a) is a diagram explaining a displacement in the y
axis direction due to a temperature change in a conventional
optical pickup, and FIG. 5(b) is a diagram explaining a
displacement in the y axis direction due to a temperature change in
the optical pickup according to the second embodiment of the
present invention;
[0096] FIG. 6 is a diagrammatic explanatory drawing showing a
configuration of the vicinity of a light source portion of an
optical pickup according to a third embodiment of the present
invention;
[0097] FIG. 7(a) is an xz plane front view showing a relationship
between gradients of a light source element and a beam shaping
element of the optical pickup according to the third embodiment of
the present invention, and FIG. 7(b) is an yz plane cross-sectional
view showing a relationship between gradients of the light source
element and the beam shaping element of the optical pickup
according to the third embodiment of the present invention;
[0098] FIG. 8(a) is a plan view of another configuration example of
the beam shaping element and a mounting portion of the optical
pickup according to the third embodiment of the present invention
as seen from the zx plane, FIG. 8(b) is a front view of the other
configuration example of the beam shaping element and the mounting
portion of the optical pickup according to the third embodiment of
the present invention as seen from the yx plane, and FIG. 8(c) is a
side view of the other configuration example of the beam shaping
element and the mounting portion of the optical pickup according to
the third embodiment of the present invention as seen from the yz
plane;
[0099] FIG. 9(a) is a plan view of another configuration example of
the beam shaping element and the mounting portion of the optical
pickup according to the third embodiment of the present invention
as seen from the zx plane, FIG. 9(b) is a front view of the other
configuration example of the beam shaping element and the mounting
portion of the optical pickup according to the third embodiment of
the present invention as seen from the yx plane, and FIG. 9(c) is a
side view of the other configuration example of the beam shaping
element and the mounting portion of the optical pickup according to
the third embodiment of the present invention as seen from the yz
plane;
[0100] FIG. 10(a) is a plan view of another configuration example
of the beam shaping element and the mounting portion of the optical
pickup according to the third embodiment of the present invention
as seen from the zx plane, FIG. 10(b) is a front view of the other
configuration example of the beam shaping element and the mounting
portion of the optical pickup according to the third embodiment of
the present invention as seen from the yx plane, and FIG. 10(c) is
a side view of the other configuration example of the beam shaping
element and the mounting portion of the optical pickup according to
the third embodiment of the present invention as seen from the yz
plane;
[0101] FIG. 11(a) is a plan view of another configuration example
of the beam shaping element and the mounting portion of the optical
pickup according to the third embodiment of the present invention
as seen from the zx plane, FIG. 11(b) is a front view of the other
configuration example of the beam shaping element and the mounting
portion of the optical pickup according to the third embodiment of
the present invention as seen from the yx plane, and FIG. 11(c) is
a side view of the other configuration example of the beam shaping
element and the mounting portion of the optical pickup according to
the third embodiment of the present invention as seen from the yz
plane;
[0102] FIG. 12(a) is a plan view of another configuration example
of the beam shaping element and the mounting portion of the optical
pickup according to the third embodiment of the present invention
as seen from the zx plane, FIG. 12(b) is a front view of the other
configuration example of the beam shaping element and the mounting
portion of the optical pickup according to the third embodiment of
the present invention as seen from the yx plane, and FIG. 12(c) is
a side view of the other configuration example of the beam shaping
element and the mounting portion of the optical pickup according to
the third embodiment of the present invention as seen from the yz
plane;
[0103] FIG. 13(a) is a plan view of another configuration example
of the beam shaping element and the mounting portion of the optical
pickup according to the third embodiment of the present invention
as seen from the zx plane, FIG. 13(b) is a front view of the other
configuration example of the beam shaping element and the mounting
portion of the optical pickup according to the third embodiment of
the present invention as seen from the yx plane, and FIG. 13(c) is
a side view of the other configuration example of the beam shaping
element and the mounting portion of the optical pickup according to
the third embodiment of the present invention as seen from the yz
plane;
[0104] FIG. 14(a) is a plan view of another configuration example
of the beam shaping element and the mounting portion of the optical
pickup according to the third embodiment of the present invention
as seen from the zx plane, FIG. 14(b) is a front view of the other
configuration example of the beam shaping element and the mounting
portion of the optical pickup according to the third embodiment of
the present invention as seen from the yx plane, and FIG. 14(c) is
a side view of the other configuration example of the beam shaping
element and the mounting portion of the optical pickup according to
the third embodiment of the present invention as seen from the yz
plane;
[0105] FIG. 15(a) is a plan view of another configuration example
of the beam shaping element and the mounting portion of the optical
pickup according to the third embodiment of the present invention
as seen from the zx plane, FIG. 15(b) is a front view of the other
configuration example of the beam shaping element and the mounting
portion of the optical pickup according to the third embodiment of
the present invention as seen from the yx plane, and FIG. 15(c) is
a side view of the other configuration example of the beam shaping
element and the mounting portion of the optical pickup according to
the third embodiment of the present invention as seen from the yz
plane;
[0106] FIG. 16(a) is a plan view of another configuration example
of the beam shaping element and the mounting portion of the optical
pickup according to the third embodiment of the present invention
as seen from the zx plane, FIG. 16(b) is a front view of the other
configuration example of the beam shaping element and the mounting
portion of the optical pickup according to the third embodiment of
the present invention as seen from the yx plane, and FIG. 16(c) is
a side view of the other configuration example of the beam shaping
element and the mounting portion of the optical pickup according to
the third embodiment of the present invention as seen from the yz
plane;
[0107] FIG. 17(a) is a perspective view showing a configuration of
the vicinity of a light source portion of an optical pickup
according to a fourth embodiment of the present invention, and FIG.
17(b) is an xy plane front view showing the configuration of the
vicinity of the light source portion of the optical pickup
according to the fourth embodiment of the present invention;
[0108] FIG. 18 is an overall configuration diagram of an optical
disk drive according to a fifth embodiment of the present
invention;
[0109] FIG. 19 is a schematic perspective view showing a
configuration of a computer according to a sixth embodiment of the
present invention;
[0110] FIG. 20 is a schematic perspective view showing a
configuration of an optical disk recorder according to a seventh
embodiment of the present invention;
[0111] FIG. 21 is a schematic perspective view showing a
configuration of an optical disk player according to an eighth
embodiment of the present invention;
[0112] FIG. 22 is a schematic perspective view showing a
configuration of a server according to a ninth embodiment of the
present invention;
[0113] FIG. 23 is a schematic perspective view showing a
configuration of a car navigation system according to a tenth
embodiment of the present invention; and
[0114] FIG. 24(a) is an xz cross-sectional view showing a
configuration example of a light source portion of a conventional
optical pickup, and FIG. 24(b) is a yz cross-sectional view showing
the configuration example of the light source portion of the
conventional optical pickup.
DESCRIPTION OF SYMBOLS
[0115] 1 Laser light source [0116] 2, 2', 2'' Beam shaping element
[0117] 3 Beam splitter [0118] 4 Collimating lens [0119] 5 Erecting
mirror [0120] 6 Objective lens [0121] 6a Aperture [0122] 7 Optical
disk [0123] 8 Quarter wavelength plate [0124] 9 Lens holder [0125]
10 Light detector [0126] 11 Light source tilting holder [0127] 12
Optical axis adjustment holder [0128] 13 Mounting plate [0129] 21
Beam shaping element holder [0130] 22 Beam shaping element
retaining spring [0131] 23 Adjusting knob [0132] 25 Extension
member [0133] 2i, 2i' Light ray incident plane of beam shaping
element [0134] 2o, 2o' Light ray output plane of beam shaping
element [0135] 2im, 2im' Incident plane-side generating line of
beam shaping element [0136] 2om, 2om' Output plane-side generating
line of beam shaping element [0137] 2z Optical center line of beam
shaping element [0138] 2ic, 2ic' Base radius center point of
incident cylindrical plane of beam shaping element [0139] 2oc, 2oc'
Base radius center point of output cylindrical plane of beam
shaping element [0140] 2S Plane including optical center line of
beam shaping element [0141] 2h Fixed position of beam shaping
element [0142] 211 Contact portion (ridge line) of beam shaping
element and beam shaping element holder [0143] 212 Contact portion
of beam shaping element and beam shaping element holder [0144] 213
Contact portion (contact plane) of beam shaping element holder and
mounting plate [0145] 51 Erecting prism having two reflecting
surfaces [0146] 100 Optical head [0147] 101 Optical disk [0148] 102
Turntable [0149] 103 Clamper [0150] 104 Motor [0151] 105 Traverse
[0152] 106 Control circuit [0153] 107 Optical disk drive [0154] 110
Personal computer [0155] 112, 121, 142 Monitor [0156] 113, 143
Keyboard [0157] 120 Optical disk recorder [0158] 130, 151 Liquid
crystal monitor [0159] 131 Optical disk player [0160] 140 Server
[0161] 144 Network [0162] 150 Car navigation system [0163] 200
Optical system having at least two or more different wavelengths as
a light source
BEST MODE FOR CARRYING OUT THE INVENTION
[0164] Embodiments of the present invention will now be described
with reference to the drawings.
First Embodiment
[0165] FIG. 1(a) is a diagrammatic explanatory drawing showing a
configuration of an optical pickup according to a first embodiment
of the present invention.
[0166] In FIG. 1(a), reference numeral 1 denotes a laser light
source that emits a laser light with wavelength .lamda. (390 nm to
420 nm: a representative wavelength of 405 nm is assumed); 2 a beam
shaping element that shapes a far-field pattern of the laser light;
3 a beam splitter that splits an optical path; 4 a collimating
lens; 5 an erecting mirror that bends an optical axis; and 6 an
objective lens (optical lens). The laser light source 1, the beam
shaping element 2, the beam splitter 3, the collimating lens 4, the
erecting mirror 5 and the objective lens 6 are disposed on a same
optical base (not shown) formed by metal or resin.
[0167] Reference numeral 7 denotes an optical disk whose substrate
thickness t1 is equal to or less than approximately 0.1 mm and on
which recording/reproducing is performed by a light beam with
wavelength .lamda.. With the optical disk 7 in FIG. 1(a), only a
substrate from a light incident plane to a recording surface is
shown. In reality, the optical disk 7 is created by gluing the same
together with a protective plate so that the mechanical strength of
the optical disk 7 is reinforced and an outer shape of the optical
disk 7 is adjusted to equal 1.2 mm that is the same as a CD.
However, for brevity, a protective member is omitted from the
respective drawings of the present invention. The optical disk 7
serves as an example of the optical information recording medium
according to the present invention.
[0168] By preferably using a semiconductor laser light source as
the laser light source 1, reductions in size, weight and power
consumption may be achieved in an optical pickup as well as in an
optical information device using the same.
[0169] When performing recording and reproducing on the optical
disk 7, a blue light beam with wavelength .lamda. emitted from the
laser light source 1 is shaped by the beam shaping element 2,
reflected off of the beam splitter 3, collimated into approximately
parallel light by the collimating lens 4, has its optical axis bent
by the erecting mirror 5, and is changed to circularly polarized
light by the quarter wavelength plate 8. Subsequently, the blue
light beam is collected by the refracting objective lens 6 through
the substrate of the optical disk 7 on the information recording
surface. Moreover, as shown in FIG. 1(b), an aperture 6a
represented by the shaded portion in the diagram and which utilizes
a member covering a small end portion of the objective lens 6 is
provided on a side of the objective lens 6 opposing the quarter
wavelength plate 8, whereby incident light is aperture-limited and
then guided to the optical disk 7.
[0170] The configuration combining the beam splitter 3, the
collimating lens 4, the erecting mirror 5, the quarter wavelength
plate 8 and the refracting objective lens 6 and which collects
light rays shaped by the beam shaping element 2 onto the optical
disk 7 serves as an example of the light collecting portion
according to the present invention.
[0171] The blue light beam reflected off of the information
recording surface of the optical disk 7 follows the original
optical path in reverse (return leg) and is changed to a straight
polarized light that is perpendicular with respect to its initial
stage by the quarter wavelength plate 8, has its focal distance
extended by the collimating lens 4, transmitted through and
reflected off of the beam splitter 3, and is incident to the light
detector 10. An output of the light detector 10 is computed to
obtain a servo signal used for focal control and tracking control
and an information signal. As described above, the beam splitter 3
is an optical path branching element having a polarization
separation thin film which, with respect to a light beam having
wavelength .lamda., totally reflects straight polarized light in
one direction and totally transmits straight polarized light in a
direction perpendicular thereto. The light detector 10 serves as an
example of the detecting portion according to the present
invention.
[0172] Next, an enlarged configuration diagram of the beam shaping
element 2 of the optical pickup according to the present first
embodiment is shown in FIG. 1(c).
[0173] The beam shaping element 2 is a lens whose incident plane 2i
and output plane 2o are both configured as a cylindrical plane.
Reference character 2im represents a generating line constituted by
a set of points obtained by expanding a point on a lens plane in
the y direction when viewing the incident plane 2i from an xz cross
section, and in a similar manner, reference character 2om
represents a generating line constituted by a set of points
obtained by expanding a point on a lens plane in the y direction
when viewing the output plane 2o from an xz cross section.
Generally, when configuring the beam shaping element with two
cylindrical planes, problems such as an optical aberration are
unlikely to occur when 2im and 2om are approximately parallel to
each other.
[0174] The beam shaping element 2 performs beam shaping so that an
elliptical shape of a far-field pattern emitted from the laser
light source 1 changes to an approximately circular shape.
[0175] Particularly, as shown in FIG. 1(d), the present first
embodiment is characterized in that the beam shaping element 2
performs shaping on an elliptical cross-sectional shape of an
incident light beam with respect to the optical axis thereof so as
to approach an approximately circular shape by shortening the major
axis direction of the elliptical shape.
[0176] This produces the following effects. Firstly, the beam
shaping element 2 is an contractionary optical part that performs
shaping for contracting a light beam shape. Consequently, since the
light quantity per unit area in a peripheral portion of light
increases, the RIM intensity of light beam passing through the
approximately circular aperture Ga and which is incident to the
objective lens 6 (in this case, the ratio of the intensity at rim
with respect to an optical maximum intensity of light beam passing
through the aperture 6a) also increases.
[0177] Light shaping performed by the beam shaping element 2
desirably results in a shape after shaping that is elliptical to
the extent that the shape is not perceived as being substantially
circular.
[0178] This is due to the following reasons. That is, when the
power factor of beam shaping increases, a relative displacement
occurs between the beam shaping element and the luminous points of
the light source, which in turn causes astigmatism. Generally, the
blue-violet semiconductor laser 1 as a light source has an emission
angle of .theta.//:8.degree., .theta..perp.20.degree., and an
emission range ratio of 2.5.
[0179] Therefore, by abstaining from performing beam shaping that
results in a greater emission angle ratio or, in other words,
intense shaping that changes a beam to a perfect circular shape or
an elliptical shape in which the major and minor axes prior to
shaping replace each other, RIM intensity can be increased while
avoiding occurrences of astigmatism.
[0180] In addition, the adoption of a contractionary system enables
an optical path length of the optical system of an approach leg
from the laser light source 1 to the optical disk 7 which form the
light collecting portion to be shortened. Accordingly, an effect is
achieved in that the optical system of the optical pickup can be
downsized which, in turn, enables the optical pickup itself to be
downsized.
[0181] The approximately circular shaped beam obtained by shaping
an elliptical shape beam emitted from the laser light source 1 by
the beam shaping element 2 serves as an example of the divergent
beam having a prescribed shape according to the present
invention.
[0182] Furthermore, by configuring the present first embodiment so
that, on the approach leg, the optical path is bent by reflection
off of the beam splitter 3 and the optical path is caused to be
incident to the erecting mirror 5 from a tangential direction
(represented as T-directions in FIGS. 1(a) to 1(c)) of the optical
disk 7, the optical axis of the light beam is rotated so as to make
the light shaping direction by the beam shaping element 2 conform
to a radial direction (represented as R-directions in FIGS. 1(a) to
1(c)) of the optical disk 7.
[0183] This further achieves the following effects with respect to
increasing RIM intensity. That is, when dividing RIM intensity into
the aforementioned radial direction and the tangential direction,
by arranging the radial-direction RIM intensity to be higher than
the tangential-direction RIM intensity, the influence of reflected
light from regions outside of a recording track to become a
recording or reproducing object on the information recording
surface and, in particular, the influence of reflected light from
an adjacent recording track arranged in a track direction can be
removed and a better recording/reproducing characteristic can be
achieved. This is particularly advantageous when recording or
reproducing on a high-density disk with a narrow track pitch.
[0184] Moreover, in the present embodiment, the generating lines
2im and 2om of the beam shaping element 2 are disposed so as to be
approximately perpendicular with respect to the recording surface
of the optical disk 7.
[0185] In a conventional optical pickup, the center line of the
curvature of a cylindrical plane of a beam shaping element is not
in a perpendicular relationship with the recording surface of an
optical disk, and the beam shaping element and the optical disk are
disposed so as to have a certain gradient therebetween. In order to
increase RIM intensity, it is desirable that light rays are
collected accurately perpendicular to the recording surface of the
optical disk. However, in order to do so, the respective optical
members disposed between the beam shaping element and the optical
disk must be designed in advance in consideration of the
aforementioned gradient between the beam shaping element and the
optical disk. Consequently, it becomes difficult to design the
respective optical members disposed between the beam shaping
element and the optical disk so that light rays are collected
accurately perpendicular to the recording surface of the optical
disk.
[0186] In contrast thereto, in the present embodiment, the
generating lines 2im and 2om which are center lines of the
curvatures of cylindrical planes of the beam shaping element 2 are
disposed so as to have, in advance, a perpendicular relationship
with the recording surface of the optical disk 7. Therefore, the
respective optical members to be disposed between the beam shaping
element 2 and the optical disk 7 can be designed in an easy
manner.
[0187] As described above, with the present embodiment, an increase
in RIM intensity can be achieved by using a contractionary beam
shaping element 2 and configuring the light collecting system so as
to rotate the optical axis of the aforementioned divergent beam so
that the major axis direction in which a light collecting ratio
increases due to contractionary deformation conforms to the radial
direction of the optical disk 7.
[0188] While the use of the contractionary beam shaping element 2
is assumed in the above description, an expansional beam shaping
element such as that described in Japanese Patent Laid-Open No.
2004-247032 may be used instead. The configuration example shown in
FIG. 2(a) uses an expansional beam shaping element 2' in place of
the contractionary beam shaping element 2 shown in FIG. 1(a). As
shown in FIG. 2(b), the beam shaping element 2' is a lens whose
incident plane 2i' and output plane 2o' are both configured as a
cylindrical plane. Reference character 2im' represents a generating
line constituted by a set of points obtained by expanding a point
on a lens plane in the y direction when viewing the incident plane
2i' that is a cylindrical plane from an xz cross section, and in a
similar manner, reference character 2om' represents a generating
line constituted by a set of points obtained by expanding a point
on a lens plane in the y direction when viewing the output plane
2o' that is a cylindrical plane from an xz cross section. The
incident plane 2i' of the beam shaping element 2' and the output
plane 2o of the beam shaping element 2 differ from each other only
in their orientations, and share the same curvature. In a similar
manner, the output plane 2o' of the beam shaping element 2' and the
incident plane 2i of the beam shaping element 2 differ from each
other only in their orientations, and share the same curvature.
[0189] In addition, generating lines 2im' and 2om' of the beam
shaping element 2' are perpendicular to the generating lines 2im
and 2om of the beam shaping element 2.
[0190] When using the beam shaping element 2' arranged as described
above, since an intensity distribution on a cross section of light
beam after shaping is perpendicular to that when using the beam
shaping element 2, light beam forming a luminous spot on the
optical disk 7 is expanded in the tangential direction of the
optical disk 7 while the shape thereof prior to shaping is retained
in the radial direction. Consequently, RIM intensity in the radial
direction is retained.
[0191] In the present embodiment, from the perspectives of
assemblability and the like, the beam shaping element 2 desirably
contacts the optical base on a plane approximately parallel to the
recording surface of the optical disk 7 on a side not opposing the
optical disk 7. This is due to the following reasons.
[0192] For example, the configuration presented in Japanese Patent
Laid-Open No. 2003-178480 described in Background Art is a
configuration which only takes into consideration astigmatism
caused by a change in the distance between the beam shaping element
and a luminous point due to temperature change.
[0193] In the case of this conventional configuration, for example,
when the temperature changes, a displacement in the positional
relationship between the luminous point and the beam shaping
element may occur with respect to a direction perpendicular to the
optical axis and in which the beam shaping element has a lens
effect or, in other words, an .+-.x direction (hereinafter simply
referred to as the x direction) as shown in FIG. 24(a). Since the
beam shaping element has a lens effect in the x direction, an
occurrence of a displacement in the positional relationship between
the luminous point and the beam shaping element with respect to the
x direction causes an incline of the optical axis of a light ray
emitted from the luminous point or a displacement of the center of
the light intensity distribution in a far-field pattern of the
light ray.
[0194] Although a displacement in the positional relationship
between the luminous point and the beam shaping element may also
occur with respect to a direction perpendicular to the optical axis
and in which the beam shaping element does not have a lens effect
or, in other words, a .+-.y direction (hereinafter simply referred
to as the y direction) as shown in FIG. 24(b), since the beam
shaping element does not have a lens effect in the y direction, it
is unlikely that an occurrence of a displacement will give rise to
an optical problem.
[0195] According to the present embodiment, by adopting the
configuration described above, even if the ambient temperature of
the optical pickup changes and parts such as the optical base
expand or contract due to heat, the beam shaping element 2 will
only cause a displacement in the y direction and a displacement is
unlikely to occur in the x direction in which the beam shaping
element 2 has a lens effect exists. Therefore, an x direction
displacement in the positional relationship with the laser light
source 1 having a luminous point can be minimized even with respect
to a temperature change, and deterioration in the optical
characteristic of the optical pickup such as an inclining of the
optical axis or a displacement of the center of the light intensity
distribution of a far-field pattern can be suppressed.
[0196] The contact between the beam shaping element 2 and the
optical base need not be planar and may take the form of a
plurality of points or lines. In this case, an effect similar to
the case where the contact portion is planar may be achieved if a
plane including the points or lines is approximately parallel to
the recording surface of the optical disk 7. In this case, a
configuration is provided in which a plane formed by the contact
portion with the optical base among the exterior shape of the beam
shaping element 2 is approximately perpendicular to the generating
line 2im or 2om.
[0197] In addition, with the beam shaping element 2, while the
generating lines 2im and 2om are typically arranged to be parallel
to each other in order to prevent occurrences of astigmatism,
supposing that the generating lines 2im and 2om are not parallel to
each other, a configuration may also suffice in which the
generating line of either the incident plane 2i or the output plane
2o and, in particular, the generating line of the plane on
whichever side that plays a significant role in the beam shaping
lens effect is approximately perpendicular on the optical pickup to
the recording surface of the optical disk 7, in which case the
aforementioned effect of suppressing deterioration in the optical
characteristic of the optical pickup with respect to temperature
change may be similarly achieved.
[0198] In the aforementioned configuration in correspondence to
temperature change, the generating line direction of the beam
shaping element 2 need not necessarily be perpendicular to the
recording surface of the optical disk 7, and an angle formed
thereby may deviate from 90 degrees by .theta.z. This is because,
for example, since the influence of an x direction component due to
expansion of the optical base during a temperature change is around
sin .theta.z, such an influence is minimal and therefore can be
ignored if .theta.z is a few degrees and the same effect as a case
where the whole angle .theta. is 90 degrees can be achieved.
[0199] Furthermore, in the present first embodiment, while a case
where the beam shaping element 2 has two cylindrical planes has
been described, a similar effect can be achieved using a beam
shaping element having only one cylindrical plane.
[0200] Moreover, while the present first embodiment is configured
as described above because, on an approach leg, an emitted light
from the laser light source 1 shown in FIG. 1(a) has its optical
path bent by reflection off of the beam splitter 3 and is incident
to the erecting mirror 5 from a tangential direction, this
configuration further achieves the following effect.
[0201] FIG. 3 shows a diagrammatic explanatory drawing depicting a
configuration of an optical pickup having a general
multi-wavelength light source.
[0202] As shown in FIG. 3, in the case where light is incident to
the erecting mirror 5 from a tangential direction, with an optical
pickup constituting a pickup including a laser light source 1
having at least two or more different wavelengths and which forms a
luminous spot on an optical disk 7 using at least two or more
objective lens 6, since the optical pickup may be configured by a
triangular erecting prism 51 having at least two reflecting
surfaces when a face 5' corresponding to an erecting mirror in an
optical path of an optical system 200 having a light source of a
different wavelength is arranged to face the erecting mirror 5 as
shown in FIG. 13, an advantage is gained in that the number of
parts can be reduced. In this case, due to spatial restrictions
existing between a spindle motor supporting the optical disk 7, and
incidence to the erecting prism (mirror) 51 in a tangential
direction is advantageous.
[0203] Moreover, in the configuration according to the present
first embodiment, an adjustment achieving an increase in the radial
direction RIM intensity is possible in principle even in the case
where the major axis direction of the ellipse of the far-field
pattern of outputted light from the laser light source 1 is caused
to conform to the tangential direction instead of to the radial
direction. In this case, while a beam shaping power factor at a
level in which the major axis of the ellipse of the far-field
pattern of outputted light from the laser light source 1 is
shortened in comparison to the minor axis (the major and minor axes
are interchanged) becomes necessary, excessively increasing the
beam shaping power factor makes it difficult to design a lens with
sufficiently low aberration and makes the occurrence amount of
optical aberrations due to relative displacement of a luminous
point and the beam shaping element 2 too great. Therefore, there
may be cases where handling becomes difficult.
[0204] In addition, by making the radial direction of the optical
disk 7 conform to the major axis direction of an ellipse of a
far-field pattern of outputted light from the light source 1, the
length of the major axis with respect to the minor axis of the
far-field pattern after beam shaping changes as the beam shaping
power factor of the beam shaping element 2 changes due to lens
design. As a result, the radial direction RIM intensity can
substantially be increased.
[0205] Furthermore, in the above description, the aperture 6a is
assumed to be provided using a member that covers a small end
portion of the objective lens 6. However, as long as the objective
lens 6 is capable of limiting incident light so as to satisfy a
desired numerical aperture (as an example, 0.85 in the case of a
blue-violet laser), the aperture is not limited to any specific
shape thereof. For example, the aperture may be realized by
providing a plate-like member on an edge portion of the small end
portion of the objective lens 6, the incident plane or the output
plane, or may be formed by applying paint.
Second Embodiment
[0206] FIG. 4(a) is a diagrammatic explanatory drawing showing a
configuration of a fixing portion of a beam shaping element 2 among
a configuration of an optical pickup according to a second
embodiment of the present invention. In FIG. 4(a), like components
to that shown in FIG. 1 are assigned like reference characters and
descriptions thereof shall be omitted. In FIG. 4(a), at least a
portion of the exterior shape of the beam shaping element 2
contacts a lens holder 9 as a contact portion.
[0207] In addition, FIG. 4(b) shows an xz cross sectional diagram
and a yz cross sectional diagram of the beam shaping element 2
according to the present second embodiment.
[0208] The light source 1 is provided in a holder (not shown in
FIG. 4(a); a light source tilting holder 11 shown in FIG. 6 and the
like) provided on an optical base. In addition, a lens holder 9 is
fixed connected to the holder provided on the optical base. The
lens holder 9 serves as an example of the mounting plate according
to the present invention.
[0209] The beam shaping element 2 includes an optical center line
2z of the beam shaping element 2 with respect to the lens holder 9,
and is fixed at any of fixing points on a line 2h at which a face
2S perpendicular to the recording surface of the optical disk 7
intersects with the exterior shape of the beam shaping element
2.
[0210] As shown in FIG. 4(b), an optical center line is hereby
defined as: when the beam shaping element 2 is viewed from an xz
cross section, a line connecting a center point 2ic of a part of a
circle to become a base of a cylindrical plane on the side of an
incident plane and a center point 2oc of a part of a circle to
become a base of a cylindrical plane on the side of an output plane
2o; and when viewed from an yz cross section, although the optical
center line is a straight line since neither the incident plane nor
the output plane has a lens plane and therefore, fundamentally, an
optical center does not exist, the optical center line shall
tentatively be defined as a line bisecting the area of the yz plane
of the beam shaping element 2 and which is orthogonal to at least
either a cross section of the incident plane or the output
plane.
[0211] By adopting such a configuration, even when the optical base
retaining the beam shaping element 2 or the lens holder 9 thermally
expands due to a temperature change of the optical pickup, the beam
shaping element 2 does not cause a displacement in the x direction
and an effect of suppressing deterioration of the optical
characteristic of the optical pickup can be achieved.
[0212] FIG. 5(a) shows a diagram for describing a state of a
conventionally configured optical pickup in which a light ray from
the laser light source 1 is incident to a cylindrical plane of the
beam shaping element 2 when ambient temperature rises. FIG. 5(b)
shows a diagram for describing a state in which a light ray from
the laser light source 1 is incident to a cylindrical plane of the
beam shaping element 2 when ambient temperature rises when using an
optical pickup configured according to the present second
embodiment. Both drawings show a front view of a cylindrical plane
of the beam shaping element 2 as seen from the side of the laser
light source 1.
[0213] As shown in FIG. 5(a), with a conventionally configured
optical pickup, a fixed face of the beam shaping element 2 does not
necessarily conform to the major axis direction of a light ray
incident from the light source. As ambient temperature of the
optical pickup rises, the optical base retaining the beam shaping
element 2 or the lens holder 9 thermally expands and a displacement
of the beam shaping element 2 occurs with respect to the optical
axis from the laser light source 1.
[0214] Here, a case will be considered where displacement due to a
temperature rise occurs only in the +y direction. As shown in FIG.
5(a), while prior to a temperature rise, the beam shaping element 2
causes a light ray to incident to the center of a cylindrical plane
or, in other words, incident so that a major axis direction of the
light ray is symmetrical with respect to a generating line of the
cylindrical plane, when temperature rises and the beam shaping
element 2 is displaced in the +y direction, the light ray becomes
incident to a position to which the major axis direction thereof is
displaced with respect to the generating line of the cylindrical
plane. In other words, the position where the light ray is incident
is displaced in the major axis direction with respect to the
generating line of the cylindrical plane.
[0215] Conversely, in the case of the optical pickup shown in FIG.
5(b) which is configured according to the present second
embodiment, since the position at which the beam shaping element 2
is fixed is arranged to be a position perpendicular to the major
axis direction of a light ray incident from the laser light source
1, although the position at which the light ray is incident to the
beam shaping element 2 when the temperature rises and the beam
shaping element 2 is displaced in the +y direction moves in a
direction perpendicular to the major axis of the light ray (the y
axis direction shown in FIG. 5(b)), no displacement occurs in the
major axis direction (the x axis direction shown in FIG. 5(b)).
[0216] As shown, with a conventionally configured optical pickup,
while a displacement of the beam shaping element 2 in the y axis
direction also causes a displacement of the incidence position of
the light ray in the major axis direction, with an optical pickup
configured according to the present second embodiment, since a
displacement in the y axis direction does not cause a displacement
of the incidence position of a light ray in the major axis
direction, displacement of the beam shaping element 2 in the major
axis direction can be suppressed in comparison to a conventional
case.
[0217] Additionally, in the present second embodiment, when fixing
the beam shaping element 2 to the lens holder 9 using an adhesive
applied to a face, as long as the adhesive is applied so as to be
approximately bilaterally symmetrical with respect to a generating
line of the beam shaping element 2, substantial fixing points will
be equivalent to those existing on 2h and the effects shown in the
present second embodiment can be similarly achieved.
[0218] Furthermore, in FIG. 4(a), while the lens holder 9 is
arranged as a symmetrical rectangular parallelepiped with reference
character 2h as a center thereof, it is more preferable to arrange
the lens holder 9 to have a symmetrical shape with reference
character 2h as a center thereof in this manner. Moreover, in FIG.
4(a), it is further preferable to have an entire side face of the
lens holder 9 fixed to the holder provided on the optical base.
[0219] Additionally, in the present second embodiment, the lens
holder 9 may alternatively be integrally formed with the optical
base. In such a case, the effect of the present second embodiment
can be similarly achieved.
[0220] Moreover, in the present second embodiment, a similar effect
to that of the first embodiment can also be achieved with a
configuration in which the face 2S is approximately perpendicular
to the recording surface of the optical disk 7.
[0221] As described above, by using the optical pickup according to
the present second embodiment, a retaining/fixing structure can be
provided in which inclining of the optical axis and displacement of
the center of light intensity distribution in a far-field pattern
are sufficiently suppressed by suppressing displacement with
respect to temperature change in a direction perpendicular to the
optical axis in addition to the occurrence amount of astigmatism
attributable to the .+-.z direction (hereinafter simply referred to
as the z direction) that is the optical axis direction.
Third Embodiment
[0222] FIG. 6 is a diagrammatic explanatory drawing showing a
structure of a light source portion among a configuration of an
optical pickup according to a third embodiment of the present
invention. In FIG. 6, like components to those shown in FIG. 1 or
FIG. 4 are assigned like reference characters and descriptions
thereof shall be omitted.
[0223] In FIG. 6, reference numeral 11 denotes a light source
tilting holder, and 12 an optical axis adjustment holder. A laser
light source 1 is fixed to the light source tilting holder 11 using
a method such as adhesion, caulking, and the like. Furthermore,
reference numeral 13 denotes a mounting plate attached to the light
source tilting holder 11 and on which the beam shaping element 2
can be mounted. In this case, the light source tilting holder 11 is
in contact with the optical axis adjustment holder 12 and is
capable of rotating approximately around a luminous point.
[0224] Through such a configuration, when the laser light source 1
has a gradient of a production emission angle or, in other words,
when the optical axis of light actually emitted from the laser
light source 1 is inclined by a prescribed angle from an ideal
optical axis, since tilting adjustment around the x axis (.theta.x)
and around the y axis (y.theta.) as shown in the diagram can be
performed by the light source tilting holder 11 with respect to the
optical axis adjustment holder 12, the emission angle can be
adjusted to a desired angle together with the entire light source
tilting holder 11. The optical axis adjustment holder 12 is in
contact with an optical base (not shown) and is provided with a
structure enabling optical axis adjustment during assembly of the
optical pickup by freely moving slidingly from side to side and up
and down.
[0225] In this case, the beam shaping element 2 is disposed so that
an exterior shape thereof comes into contact with the mounting
plate 13 attached to the light source tilting holder 11.
[0226] A relationship between a gradient of a light source whose
production gradient requires correction and an attachment gradient
of the beam shaping element 2 is shown in FIG. 7. FIG. 7(a) shows a
front view of the xz plane and FIG. 7(b) shows a cross-sectional
view of the yz plane.
[0227] As shown as an example in FIG. 7(a), in order to correct the
production gradient of the laser light source 1, even if the light
source tilting holder 11 is inclined by .theta.y from a design
ideal optical axis O, the beam shaping element 2 can be disposed so
that an optical center line 2z thereof is parallel to and overlaps
with an optical axis 1z after correction of the gradient of the
laser light source 1.
[0228] In addition, as shown in FIG. 7(b), the beam shaping element
2 is disposed such that generating line directions of the incident
plane and the output plane thereof are perpendicular to a contact
plane on which the mounting plate 13 attached to the light source
tilting holder 11 and the beam shaping element 2 contact each
other.
[0229] Through such a configuration, for example, even if the
ambient temperature of an optical pickup including the beam shaping
element 2 changes, movement of the beam shaping element 2 due to
thermal expansion of the holder member is limited to the y' and z'
directions and no displacement occurs in the x direction in which
the beam shaping element 2 has a lens effect. While the contact
portion of the beam shaping element 2 and the mounting plate 13 is
arranged as a plane, even if the contact takes the form of a
plurality of points or lines, the same effect is achieved as long
as a plane including such contact points or lines is approximately
parallel to the aforementioned contact plane.
[0230] Other examples of the beam shaping element 2 and the
mounting plate 13 will now be shown in FIGS. 8 to 16.
[0231] An example shown in FIGS. 8(a), 8(b) and 8(c) is arranged so
that a cross section of the mounting plate at the yx plane takes
the form of a V groove, whereby the beam shaping element 2 is
mounted on ridge lines 13a to be placed in line contact. Note that
FIG. 8(a) is a plan view as seen from the zx plane, FIG. 8(b) is a
front view as seen from the yx plane, and FIG. 8(c) is a side view
as seen from the yz plane. This correspondence shall be commonly
applied to FIGS. 8 to 16.
[0232] In addition, an example shown in FIGS. 9(a), 9(b) and 9(c)
is arranged so that a cross section of the mounting plate 13 at the
yx plane takes the form of a V groove, whereby the beam shaping
element 2 is mounted on protrusions 13b further provided on an
inclined face of the V groove to be placed in point contact.
[0233] Furthermore, an example shown in FIGS. 10(a), 10(b) and
10(c) is arranged so that a cross section of the mounting plate 13
at the yx plane takes the form of a V groove, whereby the beam
shaping element 2 is mounted on protruding lines 13c further
provided on an inclined face of the V groove to be placed in line
contact.
[0234] Moreover, an example shown in FIGS. 11(a), 11(b) and 11(c)
is arranged so that a side wall 13d is provided on a side face of
the mounting plate 13, whereby the beam shaping element 2 is placed
in line contact from both x and y directions with the mounting
plate 13 and the side wall 13d at respective ridge lines 13e.
Particularly, in this case, displacements in the x and y directions
can be suppressed.
[0235] In addition, an example shown in FIGS. 12(a), 12(b) and
12(c) is arranged so that a side wall 13d is provided on a side
face of the mounting plate 13, and by further respectively
providing protrusions 13f on the mounting plate 13 and on the side
wall 13d, the beam shaping element 2 is placed in point contact
from both x and y directions.
[0236] Furthermore, in an example shown in FIGS. 13(a), 13(b) and
13(c), protruding lines 13g are provided in place of the
protrusions 13f in the configuration example shown in FIG. 12,
whereby the beam shaping element 2 is placed in line contact from
both x and y directions.
[0237] Moreover, an example shown in FIGS. 14(a), 14(b) and 14(c)
is arranged such that the beam shaping element 2 is replaced by a
beam shaping element 2'' whose bottom face is a flat surface, and
by mounting the beam shaping element 2'' on a side face of the
mounting plate 13 having a side wall 13d, the beam shaping element
2'' is placed in plane contact on a contact plane 13h and in line
contact with the side wall 13d at a ridge line 13i.
[0238] Additionally, in an example shown in FIGS. 15(a), 15(b) and
15(c), protrusions 13f are provided on the side wall 13d in the
configuration example shown in FIG. 14, whereby the beam shaping
element 2'' is placed in plane contact on the contact plane 13h and
in point contact at the protrusions 13f.
[0239] Furthermore, in an example shown in FIGS. 16(a), 16(b) and
16(c), a protruding line 13g is provided on the side wall 13d in
the configuration example shown in FIG. 14, whereby the beam
shaping element 2'' is placed in plane contact on the contact plane
13h and in line contact at the protruding line 13g.
[0240] In the above configurations, arrangements of the V groove,
the side wall 13d, the protrusions 13b and 13f, the protruding line
13g are approximately parallel to the contact plane and a similar
effect to those of the configuration examples shown in FIGS. 6 and
7 can be achieved.
[0241] The above-described configurations shown in FIGS. 8 to 16
may be implemented using the optical pickups according to the first
and second embodiments.
[0242] To supplement, when the light source tilting holder 11 is
inclined by .theta.x in order to correct the production gradient of
the laser light source 1, the beam shaping element 2 mounted on the
mounting plate 13 attached to the light source tilting holder 11
concurrently also inclines by the same angle. When seen from the yz
plane, although the beam shaping element 2 operates as a flat plate
with a constant thickness and without a lens effect, since light
outputted from the laser light source 1 is diverging light,
inclining the flat plane within the diverging light causes
astigmatism.
[0243] However, using the fact that astigmatism occurs when the
distance to the luminous point deviates from a design value in the
beam shaping element 2, astigmatism attributable to the incline of
the beam shaping element 2 is able to correct by a z direction
movement of the beam shaping element 2. After the beam shaping
element 2 is fixed, even if the temperature changes, movement of
the beam shaping element 2 due to thermal expansion of the holder
member is limited to the y' and z' directions and no displacement
occurs in the x direction in which there is a lens effect. While a
displacement in the y' direction implies that the displacement is
to be further accompanied by a movement in the z direction, since
.theta.x generally ranges from 1 to 2 degrees and is therefore
small, the displacement in the z direction at this point is minimal
and is unlikely to pose a problem.
[0244] Here, in order to have the beam shaping element 2 be
self-standing in a stable manner on the mounting plate 13, the
exterior shape of the beam shaping element 2 more preferably has a
flat face for enabling plane contact with the mounting plate 13.
Obviously, the flat face of the exterior shape of the beam shaping
element 2 is structurally perpendicular to generating lines of the
incident and output planes of the beam shaping element 2.
Furthermore, the flat face of the exterior shape of the beam
shaping element 2 can also double to apply rotational regulation
during, for example, adjustment of the beam shaping element 2.
[0245] In addition, with the beam shaping element 2, while the
generating lines 2im and 2om are typically arranged to be parallel
to each other in order to prevent occurrences of optical
aberration, supposing that the generating lines 2im and 2om are not
parallel to each other, a configuration may also suffice in which
the generating line of either the incident plane 2i or the output
plane 2o, and in particular, the generating line of the face on
whichever side that plays a significant role in the beam shaping
lens effect is approximately perpendicular to a face including a
contact portion at which the mounting plate 13 attached to the
light source tilting holder 11 and the beam shaping element 2 come
into contact with each other, in which case the aforementioned
effect of suppressing deterioration in the optical characteristic
of the optical pickup with respect to temperature change may be
similarly achieved.
[0246] A similar effect can be achieved either with a mounting
plate 13 integrally formed with the light source tilting holder 11
or with a mounting plate 13 configured by a separate member and
fixed to the light source tilting holder 11.
[0247] Furthermore, in order to minimally suppress movement in the
z direction accompanying expansion/contraction of the light source
tilting holder 11 or the mounting plate 13 during a temperature
change, the beam shaping element 2 is desirably fixed to the light
source tilting holder or the mounting plate 13 by an adhesive or
the like at a position where movement in the z direction to the
luminous point is as small as possible.
[0248] Moreover, in the present third embodiment, by placing the
fixing position of the beam shaping element 2 to the light source
tilting holder 11 or the mounting plate 13 on a line that is
approximately perpendicular to a plane including an optical center
line of the beam shaping element 2 and a contact portion at which
the beam shaping element 2 comes into contact with the mounting
plate 13 attached to the light source tilting holder 11, the effect
of the present third embodiment can be further enhanced. In this
case, when the fixing position is a face of an adhesive or the
like, a higher effect can be achieved if the adhesion surfaces are
bilaterally symmetric with respect to the generating line of the
beam shaping element 2.
[0249] While the present third embodiment has been arranged so that
the direction of the generating line of the beam shaping element 2
is perpendicular to a plane including all of the contact portions
of the beam shaping element 2 and the mounting plate 13, even if an
angle formed thereby deviates from 90 degrees by .theta.z, since
the influence of an x direction component due to, for example,
expansion of the optical base or a holder member during a
temperature change is around sin .theta.z, such an influence is
small and is negligible if .theta.z is a few degrees.
[0250] Additionally, in the present third embodiment, since the
light source tilting holder 11 to which the mounting plate is
attached performs tilting adjustment around the vicinity of the
luminous point of the laser light source 1, a range of movement of
the mounting plate 13 or the beam shaping element 2 on the mounting
plate 13 accompanying such tilt operation must be taken into
consideration. In this light, a recessed portion or a though-hole
is preferably provided on the optical base so as to avoid the
movement range of the mounting plate 13 or the beam shaping element
2 on the mounting plate 13 during tilting adjustment.
[0251] Furthermore, in the present third embodiment, when reference
character .theta.x as shown in FIG. 7(b) is 0, by adopting a
configuration in which the generating line 2im or 2om of the beam
shaping element 2 is approximately perpendicular to the recording
surface of the optical disk 7, the same effect as the configuration
shown by the first embodiment can be achieved, and when .theta.x is
not 0, by adopting a configuration in which an angle formed by the
generating line 2im or 2om of the beam shaping element 2 and the
recording surface of the optical disk 7 is approximately
90.degree..+-..theta.x, the same effect as the configuration shown
by the first embodiment can be achieved.
Fourth Embodiment
[0252] FIG. 17 is an explanatory diagram showing a structure of the
vicinity of a light source among a configuration of an optical
pickup according to a fourth embodiment of the present invention.
In FIG. 17, like components to those shown in FIG. 1 to FIG. 7 are
assigned like reference characters and descriptions thereof shall
be omitted. FIG. 17(a) shows a perspective view while FIG. 17(b)
shows a front view of the xy plane shown in FIG. 17(a).
[0253] In FIGS. 17(a) and 17(b), reference character 21 denotes a
beam shaping element holder, 22 a beam shaping element retaining
spring, 23 a beam shaping element cover, and 23a an adjusting knob.
The beam shaping element cover 23 is a resin or metallic member
provided so as to cover a side face and an upper face of the beam
shaping element 2, and the adjusting knob 23a for adjustment during
assembly of the optical pickup is attached to an upper portion of
the beam shaping element cover 23.
[0254] In addition, the beam shaping element holder 21 is a resin
or metallic member provided so as to dispose the beam shaping
element 2 in a state where the beam shaping element cover 23 is
attached thereto, and is provided with a shape that covers a right
exterior wall of the beam shaping element cover 23 on a right
side-face shown in FIG. 17(b).
[0255] The beam shaping element retaining spring 22 is formed from
the mounting portion 13 to turn around to the right side-face of
the beam shaping element holder 21 and across an upper face of the
beam shaping element cover 23, and causes an elastic force directed
towards the beam shaping element 2. Accordingly, the beam shaping
element 2 is brought into pressure contact with the beam shaping
element holder together with the beam shaping element cover 23.
[0256] The beam shaping element cover 23 is fixed by adhesion to a
ceiling portion of the beam shaping element 2 at a joint surface
214.
[0257] In addition, a right side-face of the beam shaping element
cover 23 and an inner wall of the right side of the beam shaping
element holder 21 are in plane contact as a contact portion
212.
[0258] Furthermore, an inner wall of the left side of the beam
shaping element holder 21 and the beam shaping element 2 are in
line contact at a ridge line 211.
[0259] Moreover, the beam shaping element retaining spring 22 and
the beam shaping element cover 23 are in line contact at a ridge
line 215.
[0260] In addition, the contact plane, the ridge line 211 and the
ridge line 215 forming the contact portion 212 are respectively
formed so as to extend in directions parallel to the z direction in
the diagram or, in other words, directions parallel to the optical
axis of the beam shaping element 2.
[0261] Furthermore, a slit 22a is opened on an upper face of the
beam shaping element retaining spring 22, whereby the adjusting
knob 23a of the beam shaping element cover 23 is exposed to the
outside through the slit 22a. Accordingly, an adjuster of the
optical pickup is able to grasp the adjusting knob 23a and move the
beam shaping element 2 together with the beam shaping element cover
23 within the beam shaping element holder 21.
[0262] In the above configuration, the beam shaping element cover
23 serves as an example of the first outer shell portion according
to the present invention. In addition, the beam shaping element
holder 21 and the beam shaping element retaining spring 22 serve as
an example of the second outer shell portion according to the
present invention. Furthermore, the slit 22a serves as an example
of the gap according to the present invention. Moreover, the
adjusting knob 23a serves as an example of the knob portion
according to the present invention. The beam shaping element 2, the
beam shaping element holder 21, the beam shaping element retaining
spring 22 and the beam shaping element cover 23 serve as an example
of the optical element according to the present invention.
[0263] As described in the third embodiment presented above, the
beam shaping element 2 generally performs adjustment in the z
direction as shown in the drawing or, in other words, in an optical
axis direction. The structure according to the present fourth
embodiment enables adjustment of the beam shaping element 2 using
small parts and realizes a stable retaining structure.
[0264] A description will now be given. As described above, the
beam shaping element 2 receives elastic force from the beam shaping
element retaining spring 22 and is fixed inside the beam shaping
element cover 23. While an adjuster is able to move the beam
shaping element 2 by operating the adjusting knob 23a of the beam
shaping element cover 23, the beam shaping element 2 is fixed by
the contact portion 212, the ridge line 211 and the ridge line 215
which are mutually parallel along the z axis as shown in the
drawing.
[0265] Therefore, a range of movement of the beam shaping element 2
is limited only to the extension direction of the contact portion
212, the ridge line 211 and the ridge line 215 or, in other words,
to the z direction as shown in the drawing, and movement on the x y
plane perpendicular thereto is regulated.
[0266] As shown, by configuring an optical element in which the
beam shaping element 2 is movable only in an optical axis direction
thereof and by providing the optical element on a mounting plate 13
of the optical pickup according to the third embodiment, adjustment
in the x y direction as shown in the diagram and adjustment in the
z direction as shown in the diagram of an optical axis of a laser
light may be performed independently of each other.
[0267] In this case, it is possible to perform, in advance,
adjustment in the x direction in an easy manner without inclining
the beam shaping element holder 21 by .theta.y with respect to the
light source tilting holder 11 and fix the light source tilting
holder 11 and the beam shaping element holder 21, thereby enabling
x direction adjustment and z direction adjustment of the beam
shaping element 2 to be performed as independent processes.
[0268] This is particularly suitable in the following respect when
used as an optical pickup in the configuration according to the
first embodiment. That is, as was described in the first
embodiment, when increasing RIM intensity in an optical pickup,
shaping of a cross-sectional shape of light beam by the beam
shaping element 2 and rotation of the optical axis by a light
collecting system including the beam splitter 3, the erecting
mirror 5 and the like become necessary. During such adjustment,
positioning of the optical axis of the laser light outputted from
the laser light source 1 with respect to the light collecting
system is important.
[0269] With such positioning, an adjustment in the x direction as
shown in the drawing serves to prevent the emission optical axis of
the light beam incident to the optical disk 7 from bending and, as
was also described in the third embodiment, an adjustment in the z
direction as shown in the drawing is essential for cancelling
spherical aberrations that occur in accompaniment with beam shaping
by the beam shaping element 2 at the light collecting system.
[0270] However, it is extremely difficult to simultaneously perform
adjustments in both axial directions.
[0271] With an optical pickup according to the present fourth
embodiment, since adjustment in the z direction can be performed by
a sliding operation of the beam shaping element cover 23 after
adjustment in the x direction is performed beforehand by a
rotational movement operation of the light source tilting holder 11
using the configuration of the third embodiment, positioning of the
optical axis of the laser light with respect to a light collecting
system is facilitated. Therefore, the optical pickup according to
the first embodiment with increased RIM intensity can now be
readily created. In addition, there is a significant effect in that
the degree of freedom of assembly and adjustment processes of the
optical pickup can be enhanced.
[0272] Next, other characteristics of the present embodiment will
be described.
[0273] Generally, while the beam shaping element 2 is a part
moulded from glass or resin, as described above, a resin or a
metallic member is used as the beam shaping element holder 21. This
also applies to the beam shaping element retaining spring 22.
Therefore, it is conceivable that when the beam shaping element 2
contacts these members and slidingly moves, the beam shaping
element 2 may be subjected to damaged.
[0274] Therefore, in the configuration according to the present
fourth embodiment, a part of the external wall of the beam shaping
element 2 is covered by the beam shaping element cover 23 so that
sliding movement occurs between the beam shaping element holder 21
or the beam shaping element retaining spring 22 and the beam
shaping element cover 23. While the sliding movement by direct
contact between the beam shaping element 2 and the beam shaping
element holder 21 occurs at the ridge line, since this is a line
contact, occurrence of the aforementioned damage is assumed to be
sufficiently within tolerance. In addition, this enables downsizing
and simplification of the beam shaping element cover 23.
[0275] The beam shaping element holder 21 may alternatively be
configured so as to come into point contact with the beam shaping
element 2 instead of the line contact by the ridge line 211. In
this case, providing a protrusion similar to the protrusions 13b
shown in FIGS. 9, 12 and the like in the third embodiment at a
contact portion with the beam shaping element 2 shall suffice.
Furthermore, a line contact utilizing the configuration of the
protruding lines 13c as shown in FIG. 10 may also be adopted.
[0276] Moreover, by having the adjusting knob 23a protrude to the
outside, re-adjustment in the z direction against the elastic force
of the beam shaping element retaining spring 22 is also
facilitated.
[0277] Additionally, in the present embodiment, the beam shaping
element 2 is configured so that generating lines 2im and 2om of the
beam shaping element 2 are approximately perpendicular to a contact
plane 213 at which the mounting plate 13 attached to the light
source tilting holder 11 and the beam shaping element holder 21
retaining the beam shaping element 2 come into contact.
[0278] Through such a configuration, in a manner similar to the
second embodiment, displacement of the optical shaping element 2 in
the x direction due to expansion/contraction of the mounting plate
13 during a temperature change can be minimized and a structure
unlikely to cause deterioration of the optical characteristic of
the optical pickup can be realized. While the contact plane 213 of
the beam shaping element holder 21 and the mounting plate 13 is
arranged as a plane, even if the contact takes the form of a
plurality of points or lines, the same effect is achieved as long
as a plane including such contact points or lines is approximately
parallel to the aforementioned contact plane 213.
[0279] In the structure of the beam shaping element holder 21
according to the present fourth embodiment, in FIG. 17, while the
respective contact portions and ridge lines with the beam shaping
element 2 are configured so as to be bilaterally asymmetrical with
respect to the generating lines 2im and 2om of the beam shaping
element 2 as shown in FIG. 17(b), the respective contact portions
and ridge lines may alternatively be configured so as to be
bilaterally symmetrical with respect to the generating lines of the
beam shaping element 2. In this case, from a structural
perspective, a structure is realized in which the beam shaping
element 2 is completely immobile in the x direction during a
temperature change inside the optical pickup, which is even more
preferable. In essence, the contact portion according to the
present invention as the respective contact portions and ridge
lines is not limited to any disposition or specific configuration
as long as the beam shaping element can be regulated so as not to
move in a direction perpendicular to the optical axis thereof.
[0280] In addition, with the beam shaping element 2, while the
generating lines 2im and 2om are typically arranged to be parallel
to each other in order to prevent occurrences of astigmatism,
supposing that the generating lines 2im and 2om are not parallel to
each other, a configuration may also suffice in which the
generating line of either the incident plane 2i or the output plane
2o, and in particular, the generating line of the face on whichever
side that plays a significant role in the beam shaping lens effect
is approximately perpendicular to a face including the contact
plane 213 at which the mounting plate 13 attached to the light
source tilting holder 11 and the beam shaping element holder 21
retaining the beam shaping element 2 come into contact with each
other, in which case the aforementioned effect of suppressing
deterioration in the optical characteristic of the optical pickup
with respect to temperature change may be similarly achieved.
[0281] In the present fourth embodiment, when using a blue
semiconductor laser as the light source, the beam shaping element 2
is desirably made of glass from the perspectives of stability with
respect to temperature, temporal durability, and the like.
[0282] Additionally, in the present fourth embodiment, from various
perspectives including mass production and cost, improvement of
product reliability and the like, the light source tilting holder
11 and the optical axis adjustment holder 12 are desirably
constituted by a metallic material such as zinc, aluminum and the
like.
[0283] Furthermore, in the present fourth embodiment, the beam
shaping element holder 21 and the beam shaping element cover 23 are
also desirably constituted by a metallic material such as zinc,
aluminum and the like for the same reason as the light source
tilting holder 11 and the like. Desirably, paint or the like is
applied to the surface of the beam shaping element holder 21 to
increase lubricity so as to enable the beam shaping element 2 to
smoothly slidingly move on the beam shaping element holder 21.
[0284] In this case, while a lubricating paint may be applied all
over, the lubricating paint is desirably applied to at least a face
including the ridge line 211 that is a contact portion of the beam
shaping element holder 21 and the beam shaping element 2 and
respective faces corresponding to the contact portion 212 at which
the beam shaping element holder 21 and the beam shaping element
cover 23 come into contact with each other.
[0285] Moreover, when fixing the beam shaping element holder 21 and
the mounting plate 13 by adhesion, in order to prevent degradation
of the adhesiveness thereof, in regards to the surface and the
vicinity of the mounting plate 13 with respect to the beam shaping
element holder 21, the lubricating paint is desirably not applied
at this point to an adhesive application portion in the vicinity of
the contact plane 213 with the mounting plate 13 that is a surface
on the side not opposing the beam shaping element 2 and the beam
shaping element cover 23.
[0286] Additionally, in the present fourth embodiment, in order to
consistently press the beam shaping element 2 against the beam
shaping element holder 21 at a constant pressure, the beam shaping
element retaining spring 22 is desirably configured by a thin metal
having elasticity such as aluminum, stainless steel, copper, and
the like.
[0287] Furthermore, in the present fourth embodiment, while the
adjusting knob 23a has been described as being a member that is
integrated with the beam shaping element cover 23, the adjusting
knob 23a may alternatively be a separate member. In this case, from
the perspectives of downsizing and the fact that the adjusting knob
23a is to be inserted between the beam shaping element 2 and the
beam shaping element holder 21 for friction, the adjusting knob 23a
is advantageously configured by a thin metallic member of the same
or different type as the beam shaping element cover 23 to
facilitate formation of its shape.
[0288] Moreover, in the present fourth embodiment, the beam shaping
element retaining spring 22 is provided with a structure that
further simultaneously retains the mounting plate 13 attached to
the light source tilting holder 11. This enables workability during
assembly and structure stability to be further enhanced and is
therefore more preferable. However, the beam shaping element
retaining spring 22 may be configured so as to retain only the beam
shaping element holder 21 and the beam shaping element cover
23.
[0289] Additionally, in the present fourth embodiment, fixing the
beam shaping element holder 21 and the mounting plate 13 attached
to the light source tilting holder 11 by an adhesive when
performing x direction adjustment of the beam shaping element 2
enables further stabilization of the structure and is more
preferable. The light source tilting holder 11 and the mounting
plate 13 may alternatively be integrally formed. Such a structure
stabilizes the relative positions of the light source tilting
holder 11 and the mounting plate 13 and enables stability with
respect to a temperature change to be further increased.
[0290] Furthermore, in the present fourth embodiment, by placing
the fixing position of the beam shaping element 2 to the light
source tilting holder 11 or the mounting plate 13 on a line at
which a plane, which includes an optical center line of the beam
shaping element 2 and which is approximately perpendicular to a
plane including a contact portion at which the beam shaping element
holder 21 retaining the beam shaping element 2 comes into contact
with the mounting plate 13 attached to the light source tilting
holder 11, comes into contact with the exterior shape of the beam
shaping element 2, the effect can be further enhanced. In this
case, when the fixing position is a face of an adhesive or the
like, a higher effect can be achieved if the adhesion surfaces are
bilaterally symmetric with respect to the generating line of the
beam shaping element 2.
[0291] Moreover, with respect to the adhering position, in the same
manner as the second embodiment, in order to suppress movement in
the z direction accompanying expansion/contraction of the light
source tilting holder 11 or the mounting plate 13 during a
temperature change by minimum. The beam shaping element 2 is
desirably fixed to the light source tilting holder 11 or the
mounting plate 13 by an adhesive or the like at a position where
movement in the z direction to the luminous point is as small as
possible.
[0292] In this case, in the present fourth embodiment, since the
beam shaping element holder 21 exists between the beam shaping
element 2 and the mounting plate 13, it is difficult to directly
fix the beam shaping element 2 and the mounting plate 13 to each
other. Therefore, in order to fix the light source tilting holder
11 and the beam shaping element 2 to each other using an adhesive,
an extension member 25 for applying a fixing adhesive with the beam
shaping element 2 has been attached on the light source tilting
holder 11.
[0293] Fixing the beam shaping element 2 to the extension member 25
by adhesion leaves only the light source tilting holder 11, the
extension member 25, and the adhesive that fixes the two to each
other as members existing between the light source and the beam
shaping element 2, thereby enabling the influence of expansion of
the holder during a temperature change to be further reduced and
stabilized also in the z direction. Additionally, integrally
forming the light source tilting holder 11 and the extension member
25 also achieves an effect in that stability in the z direction
during a temperature change is further enhanced.
[0294] While the present fourth embodiment has been arranged so
that the direction of the generating line of the beam shaping
element 2 is perpendicular to a plane including all of the contact
portions of the beam shaping element holder 21 and the mounting
plate 13, even if an angle formed by the direction of the
generating line deviates from 90 degrees by .theta.z, since the
influence of an x direction component due to, for example,
expansion of the optical base or a holder member is around sin
.theta.z, such an influence is small and is negligible if .theta.z
is a few degrees.
[0295] Additionally, in the present fourth embodiment, in a case
where the light source tilting holder 11 has a gradient .theta.x as
shown in FIG. 7(b) in the third embodiment, when .theta.x is 0, by
adopting a configuration in which the generating line 2im or 2om of
the beam shaping element 2 is approximately perpendicular to the
recording surface of the optical disk 7, the same effect as the
configuration presented in the first embodiment can be achieved.
Furthermore, even in a case where .theta.x is not 0, if an angle
formed by the generating line 2im or 2om of the beam shaping
element 2 and the recording surface of the optical disk 7 is
approximately 90.degree..+-..theta.x, the same effect as the
configuration presented in the first embodiment can be achieved
[0296] Moreover, in the present fourth embodiment, since the light
source tilting holder 11 to which the mounting plate is fixed
performs tilting adjustment around the vicinity of the luminous
point of the light source, a range of movement of the mounting
plate 13 or the beam shaping element holder 21 on the mounting
plate 13 accompanying such a tilt operation must be taken into
consideration. In this light, a recessed portion or a though-hole
is preferably provided on the optical base so as to avoid the
movement range of the mounting plate 13 or the beam shaping element
holder 21 on the mounting plate 13 during tilting adjustment. In
this case, an optical base refers to a member for disposing the
respective optical parts configuring the light collecting systems
shown in FIGS. 1 and 3.
Fifth Embodiment
[0297] Furthermore, a description will now be given on an optical
information device according to a fifth embodiment of the present
invention which uses an optical pickup according to the present
invention.
[0298] FIG. 18 shows an overall configuration diagram of an optical
disk drive 107 as an example of an optical information device
according to the present fifth embodiment.
[0299] An optical disk 101 is fixed being sandwiched between a
turntable 102 and a clamper 103, and is rotated by a motor
(rotating system) 104. An optical head 100 having an optical pickup
according to the present invention described in any of the first to
fourth embodiments is placed on a traverse (transfer system) 105 so
as to enable light to be emitted to move from an inner periphery to
an outer periphery of the optical disk 101. A control circuit 106
performs focus control, tracking control, traverse control,
rotational control of the motor, and the like based on a signal
received from the optical head 100. In addition, the control
circuit 106 also performs reproduction of information from a
reproduction signal and transmission of a recording signal to the
optical head 100.
[0300] The control circuit 106 serves as an example of the
electrical circuit according to the present invention.
Sixth Embodiment
[0301] FIG. 19 shows a schematic perspective view of a computer
according to a sixth embodiment of the present invention equipped
with the optical disk drive (optical information
recording/reproducing device) according to the present invention
described in the fifth embodiment.
[0302] In FIG. 19, a personal computer 110 includes the optical
disk drive 107 according to the fifth embodiment, a keyboard 113
for inputting information, and a monitor 112 for displaying
information. In addition, the computer 110 is provided with a
computing device that performs computations based on information
inputted from the keyboard 113 and on information reproduced from
the optical disk drive 107.
[0303] The keyboard 113 serves as an example of the input device or
the input terminal according to the present invention, while the
monitor 112 serves as an example of the output device or an output
terminal according to the present invention.
[0304] The computer 110 according to the present sixth embodiment
equipped with the optical disk drive 107 according to the fifth
embodiment described above as an external storage device has the
effect of being capable of stably recording or reproducing
information on various types of optical disks and being usable in a
wide range of applications.
[0305] Taking advantage of its large capacity, the optical disk
drive 107 is capable of performing data backup of a hard disk
inside the computer 110, and taking advantage of the fact that
media (optical disk) is inexpensive, highly portable, and has
compatibility in that information is readable by other optical disk
drives, the optical disk drive 107 enables programs or data to be
exchanged with others and to be carried along for personal use. In
addition, recording/reproducing of existing media such as a DVD or
a CD can also be accommodated.
Seventh Embodiment
[0306] FIG. 20 shows a schematic perspective view of an optical
disk recorder (video recording/reproducing device) according to a
seventh embodiment of the present invention equipped with the
optical disk drive (optical information recording/reproducing
device) according to the present invention described in the fifth
embodiment.
[0307] In FIG. 20, an optical disk recorder 120 according to the
present seventh embodiment incorporates the optical disk drive 107
(not shown) according to the fifth embodiment, and is used
connected to a monitor 121 for displaying recorded video. In
addition, the optical disk recorder 120 is provided with an
image-to-information encoder which converts image information into
information to be recorded by the optical disk drive 107.
[0308] The optical disk recorder 120 serves as an example of the
optical information media recorder according to the present
invention.
[0309] The optical disk recorder 120 equipped with the optical disk
drive 107 according to the fifth embodiment described above has the
effect of being capable of stably recording or reproducing video on
various types of optical disks and being usable in a wide range of
applications.
[0310] The optical disk recorder 120 is capable of recording video
on a medium (optical disk) and reproducing the same whenever
convenient. With the optical disk recorder 120, a rewinding
operation as is the case with a tape is not required after
recording or reproduction, and chasing playback in which an initial
portion of a program is reproduced while the program is being
recorded or simultaneous recording playback in which a previously
recorded program is reproduced while another program is being
recorded becomes possible. Taking advantage of the fact that media
is inexpensive and highly portable, and has compatibility in that
information is readable by other optical disk drives, a recorded
video can be exchanged with others or carried along for personal
use. In addition, recording/reproducing of existing media such as a
DVD or a CD can also be accommodated.
[0311] While a case has been described where the optical disk
recorder 120 is only provided with the optical disk drive 107, the
optical disk recorder 120 may include a built-in hard disk or may
incorporate video tape recording/reproducing functions. In such a
case, videos can be temporarily saved and backup can be performed
in an easy manner.
Eighth Embodiment
[0312] FIG. 21 shows a schematic perspective view of an optical
disk player (video reproducing device) according to an eighth
embodiment of the present invention equipped with the optical disk
drive (optical information recording/reproducing device) according
to the present invention described in the fifth embodiment.
[0313] In FIG. 21, an optical disk player 131 according to the
present eighth embodiment provided with a liquid crystal monitor
130 incorporates the optical disk drive 107 (not shown) according
to the fifth embodiment, and is capable of displaying video
recorded on an optical disk onto the monitor 130. In addition, the
optical disk player 131 is provided with an information-to-image
decoder that converts information signals obtained from the optical
disk drive 107 into images. The optical disk player 131 serves as
an example of the optical information media player according to the
present invention.
[0314] The optical disk player 131 equipped with the optical disk
drive 107 according to the fifth embodiment described above has the
effect of being capable of stably reproducing video on various
types of optical disks and being usable in a wide range of
applications.
[0315] The optical disk player 131 is capable of reproducing video
recorded on a medium (optical disk) whenever convenient. With the
optical disk player 131, a rewinding operation as is the case with
a tape is not required after reproduction, and reproduction may be
performed by accessing an arbitrary address in a video. In
addition, reproduction of existing media such as a DVD or a CD can
also be accommodated.
Ninth Embodiment
[0316] FIG. 22 shows a schematic perspective view of a server
according to a ninth embodiment of the present invention equipped
with the optical disk drive (optical information
recording/reproducing device) according to the present invention
described in the fifth embodiment.
[0317] In FIG. 22, a server 140 according to the present ninth
embodiment includes the optical disk drive 107 according to the
fifth embodiment, a monitor 142 for displaying information, a
keyboard 143 for inputting information, and is connected to a
network 144.
[0318] The server 140 serves as an example of the optical disk
server according to the present invention. In addition, a terminal
of the server 140 connected to the network 144 serves as an example
of the input/output terminal that exchanges information with the
outside according to the present invention.
[0319] The server 140 equipped with the optical disk drive 107
according to the fifth embodiment described above as an external
storage device has the effect of being capable of stably recording
or reproducing information on various types of optical disks and
being usable in a wide range of applications.
[0320] Taking advantage of its large capacity, in response to a
request from the network 144, the optical disk drive 107 transmits
information (images, audio, video, HTML documents, text documents,
and the like) recorded on an optical disk. In addition, the optical
disk drive 107 records information sent from the network into a
requested location. Furthermore, since information recorded on
existing media such as a DVD, a CD or the like can also be
reproduced, information contained therein can also be
transmitted.
Tenth Embodiment
[0321] FIG. 23 shows a schematic configuration diagram of a car
navigation system according to a tenth embodiment of the present
invention equipped with the optical disk drive (optical information
recording/reproducing device) according to the present invention
described in the fifth embodiment.
[0322] In FIG. 23, a car navigation system 150 according to the
present tenth embodiment incorporates the optical disk drive 107
(not shown) according to the fifth embodiment, and is used
connected to a liquid crystal monitor 151 for displaying
topographical information or destination information. In addition,
the car navigation system is provided with an information-to-image
decoder that converts information signals obtained from the optical
disk drive 107 into images.
[0323] The car navigation system 150 equipped with the optical disk
drive 107 according to the fifth embodiment described above has the
effect of being capable of stably recording or reproducing video on
various types of optical disks and being usable in a wide range of
applications.
[0324] The car navigation system 150 determines a current position
based on map information recorded on a medium (optical disk) and on
information from a global positioning system (GPS), a gyroscope, a
speedometer, an odometer and the like, and displays the position on
the liquid crystal monitor 151. In addition, when a destination is
inputted, an optimum route to the destination is determined based
on map information or road information and displayed on the liquid
crystal monitor 151.
[0325] By using a large capacity optical disk in order to record
map information, a wide area can be covered by a single disk to
provide detailed road information. Additionally, information on
restaurants, convenience stores, gas stations and the like
associated with the vicinity of the road can be concurrently stored
in the optical disk to be provided therefrom. Furthermore, while
road information becomes outdated and removed from reality as time
elapses, since optical disks are interchangeable and media is
inexpensive, up-to-date information can be obtained by replacing
with a disk containing new road information. Moreover, since
recording/reproduction of existing media such as a DVD, a CD and
the like is also accommodated, it is also possible to watch a movie
or listen to music while in a vehicle.
[0326] As described above, by using the optical pickup according to
the present invention, an advantageous effect can be achieved in
that light use efficiency is improved and high-speed recording,
dual layer disks and the like can be accommodated. At the same
time, an effect can be achieved in that performance with respect to
changes in the temperature or environment of the optical pickup is
enhanced.
[0327] The optical pickup according to the present invention may be
utilized in a wide range of industrial fields from computers to
audio-video equipment using optical disks, and its industrial
applicability is extremely wide and extensive.
INDUSTRIAL APPLICABILITY
[0328] The optical pickup, the optical element, the optical
information device, the computer, the optical information medium
player, the car navigation system, the optical information medium
recorder and the optical disk server according to the present
invention have an effect that adjustment and enhancement of RIM
intensity using a beam shaping element is possible, and is useful
in a wide range of industrial fields from computers to audio-video
equipment using optical disks.
* * * * *